dd <- read.table("Caffeine.txt",header=T)
attach(dd)
rr <- DitheredDotPlot(dose,fingertaps,3) # siehe unten

par(mai=c(0.5,0.5,0.05,0.05))

plot(rr$X, rr$Y, pch=19,cex.axis=1.2,xaxp=c(0,200,2), xlab="", ylab="",xlim=c(-10,210))

ll <- lm(fingertaps ~ dose)
a <- ll$coefficients[1] # intercept
b <- ll$coefficients[2] # slope
xx <- c(-10,210)
yy <- a + b*xx
lines(xx,yy)


DitheredDotPlot <- function(X,Y,wd=1)
{
	tmp <- sort(X,index.return=T)
	Xd <- tmp$x
	Yd <- Y[tmp$ix]
	G <- c(0, which(Xd[1:(length(X)-1)] < Xd[2:length(X)]), length(X))
	for (i in 2:length(G))
	{
		tmp <- (G[i-1]+1):G[i]
		Yd[tmp] <- sort(Yd[tmp])
		rr <- lm(tmp ~ as.factor(Yd[tmp]))
		Xd[tmp] <- Xd[tmp] + wd*rr$residuals
	}
	return(list(X=Xd,Y=Yd))
}